In the art of compensating a beam it is necessary to compensate for phase variations within the laser generating the beam and also for distortion within the atmosphere through which the beam propagates. It is conventional to use two deformable mirrors in the path of the laser beam. One deformable mirror adjusts to compensate the phase errors resulting from propagation through the beamtrain--from the laser source to the sampling optic via utilization of a wavefront sensor-reconstructor combination. A beam from a beacon is sampled and directed to a second wavefront measuring system coupled to a controller and a second deformable mirror. A well known draw back of these systems is that the two beams do not travel the same path and so the compensation can never be fully complete. Further, both deformable mirrors must be capable of withstanding the relatively high power laser beam and are thus more expensive than more conventional low-power optics. FIG. 2 shows a conventional system, in which two separate deformable mirrors and two separate wavefront measuring systems are used. As can be seen, there is no path that is common to both of the wavefront systems.